Fair Value (Quantitative Information) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	$ (8)	$ 16	$ (341)	$ (225)	$ (221)	$ (93)
Interest rate derivatives [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(103)	(63)	(412)	(297)	(281)	(128)
Interest rate derivatives [Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Subsidiaries' credit risk	5.21%
Foreign Currency Embedded Derivative Argentine Peso [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	97
Foreign Currency Embedded Derivative Argentine Peso [Member] | Minimum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 3 years	22.14
Foreign Currency Embedded Derivative Argentine Peso [Member] | Maximum [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 3 years	39.05
Foreign Currency Embedded Derivative Argentine Peso [Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Argentine Peso to U.S. Dollar currency exchange rate after 3 years	31.72
Foreign Currency Embedded Derivative Euro [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(5)
Foreign Currency Embedded Derivative Euro [Member] | Weighted Average [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Subsidiaries' credit risk	5.21%
Foreign Currency Embedded Derivative Other [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	(1)
Commodity And Other Embedded Derivative Other [Member]
Fair Value Derivative Assets Liabilities Measured On Recurring Basis Unobservable Inputs [Abstract]
Fair Value	$ 4